Brake for automotive vehicles



Dec. 31, 1935. H M, RQCKWELL 2,026,401

BRAKE FOR AUTOMOTIVE VEHICLES Original Filed April 8, 1930 2 Sheets-Sheetv l INVENTOR.

De- 31, 1935-. H. M. RocKwELl.

BRAKE FOR AUTOMOTIVE? VEHICLES Original Filed April 8, 1930 2 Sheets-Sheet 2 VVV V dllllj..

INVENTOR.

` Patented Dec. 31, 1935 UNITED STATES PATENT oFFicE 21 Claims. (Cl. 18S-79.5)

lo ing speeds and congested traiiic conditions has emphasized the importance of efficient brakes in automotive vehicles. Therefore, most brakes are provided with means of one kind or another to permit manual adjustment from time to time as the brake band linings become worn. Unless these adjustments are made, the parts of the brake system will have certain lost motions which Very substantially reduce the eiiiciency of the brakes. Furthermore, if the adjustments are not skilfully 2O made, they may result in a lack of equalization, a condition which in itself is dangerous. In many instances, these adjustments are entirely neglected because the parts are not easily accessible. But these and other objectionable features of the prior art are overco'ine by the present invention, which has for one of its principal objects the provision of a novel and simplifiedmechanism for automatically adjusting the brakes to compensate for wear and to prevent lost'motion.

'30 By eliminating lost motion, a greater leverage can be obtained or employed, contributing further to the efliciency of the whole brake system.

In one aspect, the invention is an improvement on the mechanism disclosed in my pending application led September 10, 1927, Serial Number 218,657, the present application being T a re-ling of my' application Serial Number 442,639, led April 8, 1930. I

Other objects, features and advantages of the invention will be readily apparent from the following description in connection with the accompanying drawings, wherein one form of the invention has been shown by, way of illustration, and wherein .45 Figure 1 is an end view, partly. broken away Figure 5 is a transverse, sectional view of the same, substantially on line 5-5 of Figure 1;

Figure 6 isa View similar to Figure 4, with the brake applied, and

Figure 7 is a view similar to Figure 5 but with the brake applied as in Figure 6.

Figure 8 is a fragmentary sectional view taken cn line v8--8 of Figure 1.

The invention has been shown in the drawings as applied to a brake of the internal expanding band type, but it is not limited in this respect, since its salient features may be employed in other types of brakes with equal advantage. The brake includes a rotatable brake drum I0, having an annular peripheral flange Il within which is a brake band I2, the outer face of which is lined with friction material I3 for engaging the inner surface of the flange II. The drum I0 may be secured to some suitable rotatable element, such as an automobile wheel I4, while the band I2 is held against rotation and adapted for alternate expansion and contraction to eng-age or disengage the brake drum ange II.

The brake band I2 may be of any desired type, that illustrated being in the nature of a split ring of cast iron having suilicient inherent resiliency to retract afterrthe expanding 4pressure has been relieved.'l Intermediate its ends, the brake band is formed with a pair of spaced lugs I5 which straddle and engage opposite sides of an anchor post I6 extending inwardly from a xed annular dust plate or brake support I1. This brake support I1 is so proportioned and arranged as substantially to cover the inner side of the brake drum, and it carries suitably spaced spring ngers or guides I8, the free ends of which engage inwardly extending lugs I9 on the brake band, whereby to prevent axial movement of the brake band with reference to the brake drum. As previously stated, the brake band tends to contract, whereby to be normally disengaged from the brake drum flange I I, but it is limited in such retraction, and is supported in a substantially central position by stop units 20 at spaced intervals, as best shown in Figure 1. The stop units 20 are mounted upon the brake support Il, and

- as they constitute the principal feature of the invention, they will be hereinafter described in detail.

Any desired brake actuating means may be employed, that illustrated being hydraulically operated and including a pressure cylinder 22, which is secured to the supporting member I1 adjacent the spaced ends 23 of the brake band. Pistons 24 are slidably mounted in the opposite Cil ends of the cylinder 22 and maintained in spaced relation by a light compression spring 25 and by pressure fluid, such as oil. The iiuid space 2G between the pistons is in constant communication with a master cylinder, as usual, through an oil conduit 21, and by increasing or decreasing the fluid pressure in the master cylinder, the brake band may be expanded or contracted respectively to apply or to release the brake.. Adjacent its ends 23, the brake band is provided on its inner side with arms 28, the ends of which are rounded and in opposition to each other, and are disposed in the opposite ends of the pressure cylinder 22 and in abutting engagement with the pistons 24. In this way, outward movement of the pistons, due to increased iiuid pressure, is transmitted to the brake band to expand the same.

Referring again to the brake band stop units 20, it will be noted that there are three such units illustrated in the drawings, equidistantly spaced, but any other number of them may be employed if desired, and as they are all alike in structure, a detailed description of only one of them will be sufiicient for a complete understanding of the invention. By reference particularly to Figs. 3 to 7, it will be seen that each unit 2D comprises an automatically adjustable stop 30 in the nature of a spiral or convolute cam, the edge of which is always in contact with the inner periphery of the brake band I2. This stop or cam 30 is formed of a iiat metal plate, and has a central opening 3| by virtue of which it is rotatably mounted upon a cylindrical end portion 32 of a sleeve 33. A snap ring 34 seats in a groove 35 in said cylindrical portion to maintain the stop or cam 30 squarely against a shoulder 33a. on the sleeve 33.

As previously stated, the edges of the stops or cams 3U are always in contact with the inner periphery of the brake band I2, but since the brake band is capable of expanding and contracting, it is necessary to provide for corresponding movements of the stops. This is accomplished by mounting each sleeve 33 rockably upon an annular ange 35a which is formed intermediate the ends of a supporting post 36. The periphery of this ange is curved longitudinally, as best shown in Figs. 5 and 7, and fits somewhat loosely within a bore 31 in the sleeve 33, the end of which is spun over as at 38 to retain the sleeve on the post. Rearwardly of the ange 35a, the post has an anchoring flange 39 and a screwthreaded shank 4I] which, in cooperation with a washer 4| and a clampirTg nut-42, serve to secure the post to the supporting member I1. Thus the threaded shank 4U extends through a clearance hole 43 `in the member |1 with its axis substantially parallel with that of the brake drum, and it may be held against rotation by any suitable means. If desired, a yielding dust Washer 48 of felt or other suitable material may be disposed between the front face of the flange 39 and the spun end 38 of the sleeve.

Forwardly of the flange 35a, the post 36 is of slightly reduced diameter, and is provided with a transverse bore 58 constituting a socket for the reception of one end of a coiled compression spring 5|, the other end of which bears against one side of the inner portion of the sleeve bore 31. 'This inner portion of the sleeve bore 31 is of a diameter greater than that of the corresponding adjacent end of the post 36, and the difference between these two diameters .is substantially equal to the amount of radial movement of the brake band in expanding and contracting. Now, the bore 50 and spring 5| of each of the take-up units are disposed radially with reference to the axis of the brake drum, and in 5 such a way that when the brake band I2 is in its released position (Figs. 1, 4 and 5) the. spring 5| will be compressed. In this condition the free end of the sleeve 33 is thrown slightly oil? center but limited by the abutment of the interior 10 of the sleeve with the exterior of the post 36. As the brake is applied, however, by expanding the brake band, the spring 5| acts to throw the sleeve 33 off center in the opposite direction (Figs. 6 and 7 and thus to maintain the cam 30 l5 in engagement with the brake band.

In order that the brake may always be applied With the same amount of movement, it is necessary to compensate for wear of the brake band lining I3. This is accomplished by a torsion 20 spring 53 which surrounds the sleeve 33 and has its free end 54 engaging a shoulder 55 on the cam 30 whereby to tend to normally turn said cam and maintain it in a definite frictional relationship with the brake band. The other end 55 of the torsion spring 53 is anchored in a slot 51 at one side of the clearance hole 43 and also passes through a notch 58 in the flange 39, whereby to lock the post 36 against rotation.

The take-up unit 20 which is diametrically 30 opposed to the pressure cylinder 22, is of the same construction as the others, with the exception that its stud, sleeve and torsion spring are disposed within the anchor post I6, which prevents rotation of the brake band. 35

The structure and operation of the invention should be clearly understood from the foregoing description, and so only a brief recapitulation will be resorted to. In the normal position of rest, that is with the brake released, the brake band 40 lining I3 is entirely out of contact with the inner periphery of the brake drum flange II, by reason of the fact that the brake band I2 is contracted. The cam members 30 of the several units 28, in cooperation with the sleeves 33 and posts 36, 45 support the brake band in substantially central position, and limit its contracting movement. The clearance provided between the post 36 and the sleeve 33 determines the brake shoe clearance maintained by the device. 50

As the uid pressure is increased within the cylinder 22, the pistons 24 move apart and act upon the opposed arms 28 to expand the brake band I2 and thus to apply the brake. As the brake band I2 thus expands, the compression 55 springs 5| serve to rock their respective sleeves 33 upon the supporting anges 35 and thus permit the stop cams 30 to follow the brake band and to maintain their definite relationship. After continued use, the brake band lining will, 60 of course, become worn, tending to increase the clearance, whereupon the cams 30 will automatically be slightly rotated by their respective torsion springs 53 and thus adjusted to compensate for such wear, the cams being constantly maintained in engagement with the brake band. Hence, the brake band clearance will always be maintained at its predetermined value, and as a result, the braking eiciency of the system will be kept up to its maximum.

From the foregoing it is evident that an important advance has been made in the art to which this invention relates, by providing means for automatically adjusting the brakes as they become worn, and thus maintaining a deiinlte clearl 5 ance between the brake band land the brake drum. The arrangement is extremely simple, lending itself to economical production and to dependability in service. Obviously, the invention is susceptible of numerous modifications in the details of construction and arrangement of parts, and the right is herein reserved to make such changes as fall within the scope of the appended claims, without departing from the spirit 'of the invention.

Having thus described my invention, what I." claim is: l.

1. In a brake, a rotatable brake drum, a'brake band adapted to be alternately engaged with and` disengaged from said brake drum, and a plurality of spaced stop members to limit the disengaging movement of the brake band to maintain a prede- Y termined clearance, said stop members havingr limited floating movement in radial directions and being in constant engagement with the brake band.

2. In a brake, a rotatable brake drum, a brake band adapted to be alternately engaged with and disengaged from said brake drum, and a plurality of spaced stop members to limit the disengaging movement of the brake band to maintain a predetermined clearance, said stop members having limited oating movement in radial directions and being in constant engagement with the brake band and being automatically adjustable to compensate for wear of the brake band.

3. In a brake, a rotatable brake drum, a brake band adapted to be alternately engaged with and disengaged from said brake drum, and a plurality of stop members to limit the disengaging movement of the brake band to maintain a predetermined clearance, each of said stop members being in the nature of an automatically adjustable cam which is in constant engagement with the brake band, and adapted to compensate for.

Wear of the brake band, and each of said stop cams having limited floating movement in radial directions within the normal operating clearance.

4. In a brake, a rotatable brake drum, a b-rake band adapted to be alternately engaged with and disengaged from the brake drum, and a plurality of slack take-up units radially spaced about the brake drum, each of said take-up units comprising a spring-actuated cam in constant frictional engagement with the brake band to` limit the disengaging movement thereof, whereby to maintain -a predetermined clearance.

5. In a brake, a rotatable brake drum, an expansible and retractible brake band disposed within the brake drum, and a plurality of automatically adjustable camsfor limiting the retraction of the brake b-and to a predetermined clearance, said cams being rotatable about axes which are substantially parallel with that of the brake drum, and said cams being adapted to float Within limits whereby to maintain constant contact With the brake band.

` 6. In a brake, a rotatable brake drum, a brake band adapted to be alternately engaged with and disengaged from said brake drum, and an automatically adjustable cam for limiting the disengaging movement of the brake band to maintain a predetermined clearance, said cam being in constant engagement with the brake band.

'1. In a brake, a rotatable brake drum, a brake band adapted to be alternately engaged with and disengaged from said brake drum, a cam to engage the brake band to limit the disengaging movement thereof, means .for maintaining the cam in constant engagement with the brake band,

and automatic means for adjusting the cam to compensate for wear of the brake band.

8. In a brake, a rotatable 'brake drum, a brake band adapted to bealternately engaged with anddisengaged from said brake drum, an abutment 5 -member to limit the disenga'ging movement of the brake band, means fory rotatably adjusting the abutment member to compensate for Wear of the brake. band, and means for automatically eiecting radial ymovement of the abutment member to 1o maintain its contact with the brake band during actuation thereof. y

9. In a brake, a, rotatable brake drum, a brake band adapted to be alternately engaged Withk and disengaged from said brake drum, an abutment member to limit the disengaging movement of the brakev band, said abutment member'being in the nature of a cam which is rotatable'on an axis substantially parallel with that of the brake drum, means acting upon the cam to maintain thezo latter in engagement with the brake band, and means supporting the abutment cam for limited radial movement of the cam to follow the brake band in the normal operating clearance.

10. In a brake, a rotatable brake drum, a brake band adapted to be alternately engaged with and disengaged from said brake drum, an abutment member to limit the disengaging movement of the brake band, said abutment member being in the nature of a cam which is rotatable on an axis vsubstantially parallel withA that of the brake drum,

means acting radially upon the cam to maintain the latter in engagement with the brake band. means supporting the cam for radial movement to follow the brake band in the normal operating clearance, and means for automatically rotating the cam to maintain the clearance Within predetermined limits and to compensate for Wear of the brake band. 1l. In combination with a brake having a ro- 40 tatable brake drum and a cooperating brake band. an automatic slack take-up unit, comprising a fixed post adjacent the brake band, a stop member rotatably mounted on said post, a torsion spring surrounding a portion of the post and acting on the stop member to keep it in engagement with the brake band, and means for automatically effecting radial movement of the stop member with reference to the post as the brake band is applied or released.

l2. In combination with a brake having a rotatable brake drum and a cooperating brake band,

van automatic slack take-up unit comprising a xed post or stud extending into the plane of the brakedrum, said post or stud having an annular flange intermediate its ends, a sleeve mounted on the stud and having a limited radial rocking movement on said flange which functions as a pivot point, a compression spring extending transversely in the end of the stud and acting upon the sleeve to control the rocking movement in one direction, a cam carried by the sleeve and engaging the brake band, and a torsion spring for rotating the cam to maintain its engagement with the brake band and thus automatically to com- 65 pensate for wear of the brake band.

13. In a brake, a rotatable brake drum, a brake bandv adapted to be alternately engaged with and disengaged from said brake drum, stops to limit the released movement of the brake band, said -stops having lost motion radially equal to the desired clearance between the drum and the band when disengaged, means for maintaining the stops in a pressing contact with the brake band during the required clearance travel, andmeans for automatically adjusting the stops to compensate for wear tending to cause more than predetermined clearance, thus insuring a uniform clearance, regardless of the brake band wear.

14. In a brake, a rotatable brake drum, an expansible and retractible brake 'band disposed within the brake drum, a xed anchor member arranged intermediate the ends of the brake band to hold the brake band against rotation, and a plurality of independently automatic slack take-up units circumferentially spaced Within the brake, said take-up units being in constant engagement with the brake drum and adapted to maintain a predetermined clearance between the brake band and the drum, regardless of wear of the braking parts, and one of said take-up units being associated with the anchor member.

15. In combination with a brake having a brake drum and a cooperating brake band, an automatic slack take-up unit comprising a fixed post or stud extending into the plane of the brake drum, said post or stud having an annular flange intermediate its ends, a sleeve mounted on the stud and having a. limited radial rocking movement on said flange which functions as a pivot, a cam carried bythe sleeve and engaging the brake band, a compression spring extending transversely in the end of the stud and acting upon the sleeve to control the rocking movement in one direction and thus to maintain the cam in frictional engagement with the brake band and a torsion spring for rotating the cam to maintain its frictional engagement, said torsion spring being active only after the compression spring has taken out the predetermined clearance accompanied by a reduction in the frictional engage,- ment.

16. In combination with a brake having a rotatable brake drum and a cooperating brake band, an automatic slack take-up unit, comprising a fixed post adjacent the brake band, a stop member having limited radial movement with the brake band and being rotatable with reference to it, and a pair of springs acting conjointly to control said movements of the stop member whereby to maintain the parts of the brake in a predetermined relationship. l

17. In combination with a brake drum and a brake band, a slack take-up unit comprising a spring-actuated cam in constant frictional en- 5 gagement with the brake band to limit disengaging movement thereof, whereby to maintain a predetermined clearance.

18. In combination with a brake drum and a brake band, means for anchoring the brake band against rotation, and a. slack take-up unit associated with said anchoring means, said slack takeup unit comprising a spring-actuated cam in constant frictional engagement with the brake band to limit disengaging movement thereof, whereby to maintain a predetermined clearance.

19. In combination with a brake having a brake drum and a cooperating brake band, a plurality of automatic slacktake-up units circumferentially spaced with reference to each other and adapted to suspend the brake band in substantially central position within the brake drum, each of said take-up units comprising a fixed post adjacent the brake band, a stop member having limited radial movement with the brake band and being rotatable with reference to it, and a pair of springs acting conjointly to control said movement of the stop member whereby to maintain the parts of the brake in predetermined relationship.

20. In combination, a pair of friction surfaces adapted to be moved into engagement and out of engagement, means for limiting the clearance between the surfaces, said means including a cam. means for rotating the cam about its axis, and means for moving the cam at an angle to its axis.

21. In combination, a pair of frictional surfaces adapted to be alternately engaged and disengaged With each other, a stop member to limit the disengaging movement of the surfaces and to maintain a predetermined clearance, said stop member including a cam, means for rotating the cam axially, and means for bodily moving the cam at an angle to the axis of the cam.

HUGH M. ROCKWELL. 

